1. Field of the Invention
This invention in general relates to an electrode, and is particularly applicable to the field of the iontophoretic introduction of an ionic substance into a body, where it may be used in the manufacture of simple and reliable electrodes incorporating an improved means of storing the ionized substance within the electrode, an improved means for iontophoretic conduction of substances into the body, and improved means for attaching the electrode to the body.
2. Description of the Prior Art
Iontophoresis is a method for introducing ionic substances into a body. The method utilizes direct electrical current to drive the ionized substances, such as chemicals or drugs, through the intact skin or other body surface. This has proven to be very useful in numerous medical applications. U.S. Pat. Noss. 3,991,755 issued to Jack A. Vernon, et al and 4,141,359 issued to Stephen C. Jacobsen, et al disclose examples of iontophoretic devices and some applications of the devices. The iontophoresis process has been found to be useful in the administration of lidocaine hydrochloride, hydrocortisone derivatives, acetic acid, fluoride, penicillin, dexamethasone sodium phosphate and many other drugs. Perhaps the widest use of iontophoresis is that of diagnosing cystic fibrosis by using pilocarpine nitrate iontophoresis. The pilocarpine nitrate stimulates sweat production; the sweat is collected and analyzed for its chloride or sodium content to detect the presence of the disease.
In iontophoretic devices two electrodes are used. One electrode, called the active electrode, is the electrode at which the ionic substance is driven into the body. The other electrode, called the indifferent or ground electrode, serves to close the electrical circuit through the body. It will be appreciated by those skilled in the art that the active electrode must hold, contain, or otherwise have available to it a source of the ionic substance. Thus, in the prior art the active electrode is generally relatively complex compared to the indifferent electrode.
U.S. Pat. No. 3,991,755 discloses several examples of active electrodes. In one example the electrode comprises a stainless steel wire housed in a plastic sheath which is shaped to safely fit within the ear canal together with a liquid solution containing the ionized substance, which liquid is poured into the ear canal so that it contacts the inner ear and the wire through an opening in the sheath. In another example, the electrode wire housed in a plastic sheath having an opening is placed in a wad of absorbent material which holds the liquid containing the ionic substance.
U.S. Pat. No. 4,141,359 also discloses several embodiments of an active electrode. All of the embodiments include a receptacle for holding either a conducting gel in which the ionic substance is dissolved, or for holding a sponge which is saturated with the conductive gel in which the ionic substance is dissolved. The conducting gel/ionic drug solution communicates with the body tissue through a hole in the receptacle. The receptacle is held in contact with the skin by an adhesive pad surrounding the receptacle or a strap attached to the pad. In other embodiments of the prior art the hole in the receptacle is covered with a membrane and the ionic substance is driven through the membrane by the electric current.
An active electrode formed by a gauze pad soaked in the solution containing the ionic substance superimposed by several layers of paper towels moistened with tap water and a section of block tin or aluminum foil placed over the moistened towel with the tin or foil connected to the iontophoretic current generator by means of a wire and alligator clip is disclosed in Acetic Acid Iontophoresis for Calcium Deposits, by Joseph Kahn in Physical Therapy, Vol. 57, No. 6, June, 1977 (pp. 658-659).
The active electrodes of the prior art have a number of disadvantages. Those in which the ionic substance is held in solution in a liquid are relatively messy. Of these, those in which the liquid is not contained in an absorbent material can be used only in situations where body cavities form a natural container for the liquid, or it is necessary to employ a cup or other container to hold the liquid about the body surface through which the ionic substance can be driven. The electrodes employing the conductive gel in which the ionic substance is dissolved are somewhat less messy, but still leave a residue of gel after use. The electrodes employing the membrane alleviate most of the above problem but create additional complexities in the construction and handling of the electrode, relating both to the membrane itself and the separate means for insertion of the ionic substance that is required if a membrane is used. In all of these electrodes, a separate strap or adhesive pad is necessary to hold the electrode in place, or alternatively the patient must remain still during the use of the ionotophoretic device so that the electrode will remain in place. Even with the use of a strap or adhesive pad the portion of the electrode containing the ionic substance is still subject to some movement due to the flexibility in such materials, and the flexibility of body tissue. Moreover, in all of these devices some of the liquid or gel may move away from the main body of the liquid gel, as for example by dripping out of the absorbent material or sliding under the edge of the adhesive pad. When this occurs, electrical contact may or may not be lost and the ionic substance in the dislocated portion of the material may or may not be driven into the body. The aforementioned disadvantages all result in an inability to precisely control the area over which the ionic substance is administered, which control is often necessary for drugs and other chemical agents for which the process is used. In addition to the complexities involved in applying the electrodes mentioned above, all of the active electrodes of the prior art require complex procedures for handling the material containing the ionic substance prior to and, in some electrodes, during the iontophoretic process. A simpler electrode would permit the iontophoretic process to be much more widely applied, not only in applications now known to be practiced, but also in many new applications that previously were not practical. For example, although electrical stimulation of body tissue for pain suppression and muscular therapy have been known for some time, (see, for example, U.S. Pat. No. 4,019,518) these treatments have not, up to now, been used in combination with iontophoresis, except on a limited clinical basis, since up to now iontophoretic electrodes have been too messy and complex for use by the average patient.